Tighter Legislation

By introducing stricter legislation controlling the permitted emissions from production plants and the requirement for documented evidence that these levels are not exceeded, governments are forcing manufacturers who use organic solvents in their production processes to take action. This action may include installing emission monitoring systems, or alternatively, allowing the authorities to appoint an independent body to make spot checks. The installation of a monitoring system may at first seem costly, but it can have some definite benefits which were not considered at first.

Pharmacia in Uppsala, Sweden, use Chloroform as an extractant in the production of Healon. Even though the process takes place in a closed system, it is inevitable that some of the Chloroform vapours seep into the air in the factory. To reduce the risks to the work-force, a centralised ventilation system draws the air from the various areas in the factory to three carbon filters. After the Chloroform has been removed, the air is then expelled out of the factory through a vent. The carbon filters are used in rotation. Two filters remove the Chloroform from the air while the third is being "regenerated". This involves passing steam through the filter to remove the Chloroform. (The Chloroform is then recovered from the steam, using condensation, and then stored in barrels). Pharmacia wanted a real-time monitoring system that would monitor the amount of Chloroform in the vent emissions from the factory, be easy to operate by personnel who have little or no chemical training, and could maintain a historic database and give hard copies of this when required

A Multi-gas Monitor - INNOVA 1302 was installed. The monitor, with its photoacoustic (PAS) measurement technique is fitted with a narrow band optical filter which enables Chloroform to be measured accurately from 0.035 to >350 ppm (without needing to change filters or setups). The PAS technique makes the monitor extremely stable, (accuracy is maintained to ±5% of the reading between 1 and 100ppm of Chloroform). With up to six months between recalibrations, maintenance and running costs are kept low. To transport the samples from the sampling point to the monitor, a Multipoint Sampler - INNOVA 1309 is included. The multiplexer is able to draw samples from up to 12 different points, each up to 300 meters away. Control of the sampling and measuring procedures is done via a personal computer (PC) with Application Software - INNOVA 7300 installed. This software also presents the measurement data as graphs on screen and produces hard copies via a printer. It can be further customized by including a user-program. This enables data from the application software to be post-processed further to produce, for example, comprehensive reports or additional calculated data. Pharmacia wanted to know more than just the concentration of Chloroform in the emission gases, they wanted to know what quantity of Chloroform was emitted. An additional piece of equipment was required – a flow meter. This is installed in the ventilation duct in front of the sampling point. It measures the flow rate in the system and sends information, as analogue signals, to the personal computer. The user-program uses the flow rate and concentration data to calculate a single value for the quantity of Chloroform emitted in a time unit. This time unit is defined by the user, and in this case is a week. This system had so much in reserve that Pharmacia were able to use it to monitor various areas inside the factory to ensure the safety of their workers.